Guidance system for a horizontal drilling apparatus

ABSTRACT

A drilling apparatus for forming a horizontal borehole substantially parallel to a first drilled horizontal borehole which has a signal generating apparatus inserted into the first borehole. A horizontal drill is inserted into the subterranean strata adjacent the first drilled borehole and operated until it is in the formation. A signal receiver contained in the horizontal drill apparatus will then receive a signal generated by the signal generating apparatus. The signal generating apparatus will always be maintained a fixed distance behind or in front of the horizontal drilling apparatus. The signal receiver in the horizontal drill will also include an antenna sensitive to direction which can orient itself with the signal generating apparatus. Knowing the angle between the horizontal drill and the signal generating apparatus, along with the distance along the first borehole between the horizontal drill and the signal generating apparatus, will provide sufficient data to calculate the distance between the first horizontal borehole and the drilling apparatus.

United States Patent [191 Dahl et al.

[451 Dec. 10, 1974 1 GUIDANCE SYSTEM FOR A HORIZONTAL DRILLING APPARATUS[75] Inventors: Herbert Douglas Dahl; Tibor O.

Edmond, both of Ponca City, Okla.

[73] Assignee: Continental Oil Company, Ponca City, Okla.

22 Filed: Nov. 30, 1973 21 Appl. No.: 420,410

Primary Examiner-Henry C. Sutherland Assistant ExaminerRichard E.Favreau Attorney, Agent, or Firm-William J. Miller [57] ABSTRACT Adrilling apparatus for forming a horizontal borehole substantiallyparallel to a first drilled horizontal borehole which has a signalgenerating apparatus inserted into the first borehole. A horizontaldrill is inserted into the subterranean strata adjacent the firstdrilled borehole and operated until it is in the formation. A signalreceiver contained in the horizontal drill apparatus will then receive asignal generated by the signal generating apparatus. The signalgenerating apparatus will always be maintained a fixed distance behindor in front of the horizontal drilling apparatus. The signal receiver inthe horizontal drill will also include an antenna sensitive to directionwhich can orient itself with the signal generating apparatus. Knowingthe angle between the horizontal drill and the signal generatingapparatus, along with the distance along thefirst borehole between thehorizontal drill and the signal generating apparatus, will providesufficient data to calculate the distance between the first horizontalborehole and the drilling apparatus.

10 Claims, 3 Drawing Figures GUIDANCE SYSTEM FOR A HORIZONTAL DRILLINGAPPARATUS BRIEF DESCRIPTION OF THE PRIOR ART The closest prior artrelating the concept disclosed herein is the US. Pat. Nos. to Barrett,3,578,807 and 3,521,796, both of which relate to a tunnel diggingapparatus. A US. Pat. No. to James C. Coyne, 3,589,454, discloses asystem for controlling an underground mole in accordance with a pair ofantennae which are positioned on the surface of the earth. The patentsto Barrett disclose a method for digging a tunnel utilizing aradioactive stripe which is placed along the edge of the tunnel whichhas been dug. A radioactive sensor is mounted on the tunnel diggingmachine and picks up the radiation released by the radioactive stripe.The digging machine maintains its distance from the first formed hole bymaintaining a constant radiation being detected. The patent to Barrettalso discloses the concept of tuned radio frequency lengths, forexample, metal rods or painted stripes being placed along the tunnelwall. A signal generated by the digging machine is tuned to the rods orstripes which provide a reflected signal which is picked up by thetunnel digging machine. The patent to Coyne discloses a concept ofmounting an antenna on the surface of the earth and controlling a moleor horizontal drill in accordance with a rotating magnetic fieldgenerated by the pair of antennae.

BRIEF DISCUSSION OF THE INVENTION This invention relates to a method fordrilling a second elongated, horizontal borehole which is substantiallyparallel to a first drilled horizontal borehole by inserting ahorizontal drill into the ground along an axis parallel to the firstdrilled hole and spaced from the first hole. A signal generating meansis then positioned in the first hole a known distance with respect tothe horizontal drill. As the horizontal drill is operated, the signalgenerating means is maintained a fixed distance in the first bored holewith respect to the distance the horizontal drill has penetrated. Areceiving antenna contained in the horizontal drill determines the anglebetween the horizontal drill and the signal generating means. Knowingthe angle and knowing the distance that each device is in its respectiveborehole, the distance can be easily calculated by the use oftrigonometry.

A more nearly parallel hole can be drilled by adding a second loopantenna detector and determining a second angle. A comparison of thefirst and second angles will determine the exact orientation of thedrill with respect to the originally drilled hole.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a top sectional view takenthrough two horizontally bored holes, illustrating the signal generatingmeans and the horizontal drill;

FIG. 2 is a perspective view of the boreholes illustrating the methodfor controlling the penetration of the signal generating means withrespect to the horizontal drilling apparatus; and,

FIG. 3 is a perspective view of a signal generating means.

DETAILED DESCRIPTION OF THE INVENTION Referring to all of the figures,but in particular to FIG. 1, a formation has a bored horizontallydrilled hole 11 and a horizontal borehole 12 which is in the process ofbeing drilled by a horizontal drilling apparatus generally referred toby the number 13. A signal generating means 14 has an antenna 15 usedfor radiating a radio frequency signal. A control cable 16 is attachedto the signal generating means 14. The horizontal drill 13 generallycomprises a rotary drill 8, a deflecf tion unit 9, a drilling motor 17,which is mechanically coupled to a shaft 18, to drill 8, an instrumentpackage 19, which contains a loop antenna 20. A power mechanism 21 iscoupled to the horizontal drill and comprises a plurality of pressurefeet 22. A second portion of the power-driving mechanism 23 likewise hasa plurality of pressure feet 24. Portion 23 is connected to portion 19by a shaft 25.

A second housing 26 may be attached to the second portion 23. Cable 16Ais attached to housing 26. A second loop antenna 24 is mounted inhousing 26.

Referring to FIG. 2, the signal generating means 14 has its antenna 15mounted on the front of the housing. Along the side of the housing ispositioned a plurality of drive wheels 30. Drive wheels 30 are operablycoupled to a motor (not shown) which in turn is coupled to a powersource 31 which may, for example, be a battery. Power source 31 iscoupled through wires 32 and 33 to a pressure switch 34, which ismechanically maintained in a closed position by a spring 35. Cable 16 isconnected to switch 34 in a manner to open switch 34 if signalgenerating means 14 progresses past the length of cable 16. Power source31, however, maintains power at all times to the signal generatingsystem coupled to antenna 15.

The cable control system is illustrated in FIG. 3 and essentiallycomprises a reel coupled to a flexible cable 41 to a drive motor 42 anda reel 43 coupled to a flexible drive cable 44 to motor 42. A slipclutch 45 couples flexible cable 41 to reel 40. A cable metering systemcomprises a roll coupled through a flexible cable 51 to a second roll52. A pressure roll 53 maintains a tight pressure against cable 16A androll 52. Likewise, a second pressure roll 54 maintains a firm pressureagainst cable 16 and roll 50.

OPERATION The operation is best illustrated by referring to all of thefigures but in particular to FIG. I. As horizontal drill 13 forces itsway into formation 10, cable 16A will be pulled by the horizontal drill.As the cable is pulled, roll 52 will turn. Any rotation of roll 52 willbe transmitted through flexible cable 51 to roll 50, which will likewiserotate causing a slacking in tension of cable 11. As cable 11 slacks intension, switch 34 will close, applying power through power source 31 tothe drive motor and wheel 30. Signal source 14 will then move followingthe movement of horizontal drill 13. In the above operation then, thedistance d will always be known. As the signal is being transmitted fromantenna 15, loop antenna 20 contained in the horizontal drill instrumentpackage 19 will continue to seek the angular direction (b between thehorizontal drill and the signal generating antenna 15. When 4), isdetermined and d is determined, the distance a which represents thedistance of the horizontal drill from the signal source,

can then be determined. Since the tangent of d), is equal to Li /d suchinformation can be easily calculated and corrections as necessaryapplied to the horizontal drill to cause it to drill so as to maintain aconstant distance between borehole l1 and borehole 12. Such a controlsystem is completely described in application 419,157, filed Nov. 26,1973, titled Control System for a Drilling Apparatus, by Henry A.Bourne, Jr., and Rondon L. Schroeder, and assigned to the assignee ofthis invention. The control system basically comprises a deflection unit16 which can be positioned around the axis of drill 13 to 360. As thedrill requires deflection, the roll control rotates the deflection unit9 in a desired direction; the deflection unit then is pressed againstthe borehole wall, causing pressure on the drill in the directiondesired. The cable 16A is coupled to the drive propulsion unit portion21. Since portion 23 of propulsion unit 21 is coupled through shaft 25directly to instrument package 19, the cable will move whenever theinstrument package moves, thus always maintaining a known distancebetween the terminus of cable 16A and cable 16.

The drilling apparatus can be made to drill substantially parallel withthe previously bored hole 11 by comparing the null angle (b of thesecond loop antenna with the null angle 11 of the first antenna. Bothantennae can be fixed in position so that (1) and (1) provide a parallelhole with a predetermined distance (1,. The drill operator will thenmaintain the drill so that the null conditions are maintained.

lt is obvious, of course, that other systems can be used to couple theroller 52 to roller 50 so that the same amount of cable is played outinto both holes. For example, an electrical servo controlled system canmeasure the cable being played out in 16A and transfer electrically theinformation to roll 50. Roll 50 can then be operated to a simple circlesystem so that it will play out the same mount of cable 16. It isfurther obvious, of course, that the signal generating means 14 can beeither advanced in the hole further than antenna 20 or behind antenna20, and the system will function equally well.

It is obvious that changes can be made in the apparatus herein disclosedand still be within the spirit of the invention as described in thespecification in the appended claims.

What we claim is:

1. A method for drilling a second elongated horizontal boreholesubstantially parallel to a first drilled horizontal boreholecomprising:

a. inserting a horizontal drill into the ground along an axis parallelto a drilled hole and spaced from said first hole;

b. positioning a signal generating means in said first hole a knowndistance with respect to said horizontal drill;

c. maintaining said known distance along the axis of said first hole assaid second hole is drilled;

d. receiving said generated signal on said drill;

e. calculating the distance of said signal generated from said receiver;and

f. controlling said horizontal drill in accordance with said calculationto maintain a predetermined distance between said drill and said signalgenerating means.

2. A method as described in claim 1 wherein said signal generating meansis positioned in said first hole equal to the distance said receivingmeans is positioned in said hole being drilled.

3. A method as described in claim 1 wherein said signal generating meansis maintained a known distance with respect to said receiving means insaid borehole being drilled.

4. Apparatus for drilling a second elongated horizontal boreholesubstantially parallel to a first drilled horizontal boreholecomprising:

a. means for inserting a signal means in said first borehole;

b. horizontal drilling means;

c. means for propelling said horizontal drill means into the groundalong an axis parallel to said first drilled borehole to form a secondelongated horizontal borehole;

d. signal means in said horizontal drill means;

e. means for generating a signal in one signal means and receiving saidgenerated signal in said remaining signal means; and

f. means for maintaining said first signal means a predetermineddistance in said drilled borehole with respect to the position of saidsecond signal means in said second borehole.

5. An apparatus as described in claim 4 wherein said signal is generatedby said first-mentioned signal means and wherein said signal is receivedby said secondmentioned signal means.

6. An apparatus as described in claim 4 wherein said second-mentionedsignal means comprises:

a. a directional antenna;

b. means coupled to said directional antenna for de termining thedirection of said horizontal drill axis from said first-mentioned signalmeans; and

c. means for maintaining said first signal means a predetermineddistance from said second signal means, whereby the angle between saidfirst and second signal means can be determined and whereby the lineardistance between said first and second receiving means can be determinedso that the distance between said borehole containing said first signalmeans and the borehole being drilled containing said second signal meanscan be calculated.

7. An apparatus as described in claim 4 wherein said second-mentionedsignal means comprises:

a. first and second directional antenna means mounted on said drillingapparatus and spaced apart a predetermined distance; and,

b. means coupled to each of said first and second directional antenna todetermine its orientation with respect to said signal means in saidfirst hole.

8. An apparatus as described in claim 4 wherein said means formaintaining said first signal means a predetermined distance in saiddrilled borehole with respect to the position of said second signalmeans in said second borehole comprises:

a. a first reel having a first line stored thereon;

b. a second reel having a second line stored thereon;

c. means for connecting said first line to said firstmentioned signalmeans and means for connecting said second line to said second-mentionedsignal means; and,

(1. means for metering the lengths of said first and second lines playedout by said respective first and second reels.

9. An apparatus as described in claim 8 wherein said first-mentionedsignal means comprises a housing; means for propelling said housingalong said borehole; and, means for attaching said first line to saidhousing.

10. An apparatus as described in claim 7 wherein said means forattaching said first line to said housing comsion means.

232 33 i v UNITED STATES PATENT OFFICE -CERTIFICATE OF CORRECTION PatentNo. 3 55,355 Dated December 10, 1971+ InventoflsH. Douglas Dahl andTibor O. Edmond,

It is certified thaterror appeare in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

; Column 5, line 6 "7" shouldbe Signed and sealed this 4th day 'of March1975.-

(SEAL) ACCESC:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting;Officer and Trademarks 23 UNITED STATES PATENT omen CERTIFICATE OFCORRECTION ww 5,855,185 Dated December 10, 197A InventoflsH. DouglasDahl and Tibor O. Edmond It is certified that error appears in theabove-identified intent and that said Letters Patent are herebycorrected as shown below:

- Column 5, line "7" should be --9--.

Signed and sealed this 4th day of March 1975.

(SEAL) Attest:

C. MARSHALL DANN RUZH C. MASON Commissioner of Patents Attesting Officerand Trademarks

1. A method for drilling a second elongated horizontal boreholesubstantially parallel to a first drilled horizontal boreholecomprising: a. inserting a horizontal drill into the ground along anaxis parallel to a drilled hole and spaced from said first hole; b.positioning a signal generating means in said first hole a knowndistance with respect to said horizontal drill; c. maintaining saidknown distance along the axis of said first hole as said second hole isdrilled; d. receiving said generated signal on said drill; e.calculating the distance of said signal generated from said receiver;and f. controlling said horizontal drill in accordance with saidcalculation to maintain a predetermined distance between said drill andsaid signal generating means.
 2. A method as described in claim 1wherein said signal generating means is positioned in said first holeequal to the distance said receiving means is positioned in said holebeing drilled.
 3. A method as described in claim 1 wherein said signalgenerating means is maintained a known distance with respect to saidreceiving means in said borehole being drilled.
 4. Apparatus fordriLling a second elongated horizontal borehole substantially parallelto a first drilled horizontal borehole comprising: a. means forinserting a signal means in said first borehole; b. horizontal drillingmeans; c. means for propelling said horizontal drill means into theground along an axis parallel to said first drilled borehole to form asecond elongated horizontal borehole; d. signal means in said horizontaldrill means; e. means for generating a signal in one signal means andreceiving said generated signal in said remaining signal means; and f.means for maintaining said first signal means a predetermined distancein said drilled borehole with respect to the position of said secondsignal means in said second borehole.
 5. An apparatus as described inclaim 4 wherein said signal is generated by said first-mentioned signalmeans and wherein said signal is received by said second-mentionedsignal means.
 6. An apparatus as described in claim 4 wherein saidsecond-mentioned signal means comprises: a. a directional antenna; b.means coupled to said directional antenna for determining the directionof said horizontal drill axis from said first-mentioned signal means;and c. means for maintaining said first signal means a predetermineddistance from said second signal means, whereby the angle between saidfirst and second signal means can be determined and whereby the lineardistance between said first and second receiving means can be determinedso that the distance between said borehole containing said first signalmeans and the borehole being drilled containing said second signal meanscan be calculated.
 7. An apparatus as described in claim 4 wherein saidsecond-mentioned signal means comprises: a. first and second directionalantenna means mounted on said drilling apparatus and spaced apart apredetermined distance; and, b. means coupled to each of said first andsecond directional antenna to determine its orientation with respect tosaid signal means in said first hole.
 8. An apparatus as described inclaim 4 wherein said means for maintaining said first signal means apredetermined distance in said drilled borehole with respect to theposition of said second signal means in said second borehole comprises:a. a first reel having a first line stored thereon; b. a second reelhaving a second line stored thereon; c. means for connecting said firstline to said first-mentioned signal means and means for connecting saidsecond line to said second-mentioned signal means; and, d. means formetering the lengths of said first and second lines played out by saidrespective first and second reels.
 9. An apparatus as described in claim8 wherein said first-mentioned signal means comprises a housing; meansfor propelling said housing along said borehole; and, means forattaching said first line to said housing.
 10. An apparatus as describedin claim 7 wherein said means for attaching said first line to saidhousing comprises a pressure sensitive switch, and means for couplingsaid pressure sensitive switch to said propelling means, whereby whensaid propelling means moves said housing against the tension on saidfirst line, said pressure sensitive switch means will turn off thepropulsion means.